1. Field of the Invention:
This invention relates to a method for producing a carbon-ceramic composite material of high density and strength by a facilitated process which can be carried out under normal pressure.
Carbon-ceramic composite materials have wide applications as various high temperature materials, mechanical parts materials, ceramic materials, materials for use in chemical industries or electric or electronic materials. This invention particularly concerns a novel technology for producing a carbon-ceramic composite material, which permits automation of the manufacturing process and a continuous operation, realizing a considerable reduction of the production cost while facilitating production of articles of complicate shapes.
2. Prior Art:
Carbon-ceramic composite materials are novel materials which possess the versatile properties of ceramic materials along with excellent high temperature properties, electric conductivity, corrosion resistance and abrasion resistance which are characteristic of carbonaceous materials. Many attemps have thus far been devoted to the development of carbon-ceramic composite materials in various countries. However, it has been difficult to obtain a product of high density by the conventional methods using a pitch binder, which can be a cause of porousness, or by the conventional hot press methods, in addition to the problems such as high production cost and difficulty of producing large structures of different shapes, barring wide application of the carbon-ceramic composite materials.
In our prior patent applications (Japanese Patent Publication No. 58-38386, Laid-Open Japanese Patent Application Nos. 59-131576, 59-213674 and 60-60299), the present inventors proposed novel techniques for obtaining carbon-ceramic composite materials by mixing finely ground powder of low-temperature coke having a residual volatile content greater than 4% with ceramic powder, followed by compression molding and sintering. These methods permit sintering under normal pressure and unnecessitate a binder, so that products of high density and strength can be obtained at a significantly reduced cost as compared with the conventional hot press processes. These advantages are receiving a keen attention in various industrial fields, arousing new expectaions for carbon-ceramic composite materials.
In the inventors' prior methods mentioned above, it is invariably necessary to apply pressure when molding the raw powder mixture, more specifically, to apply a large pressure of at least 1500 kg/cm.sup.2 or higher and, in order to obtain a product of high density, to apply normally a pressure as high as 2000 kg/cm.sup.2. Besides, the pressure has to be applied uniformly over a long time period to prevent cracking of the products after molding or during the sintering process. Of course, this is unsuitable for continuous operations, and invites a considerable increase in the production cost. In addition, the molding method which necessitates application of a high pressure has a difficulty in forming structures of complicate shapes, particularly, rod-like elongated structures. In order to eliminate these problems or drawbacks, it is necessary to resort to injection molding, extrusion molding or other powder molding which does not need application of a high pressure and which is suitable for continuous operation.